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Abstract:

A method and a wireless communication system for providing downlink (DL)
control signalling for a communication apparatus are provided. In the
method, at least two scheduling cells are configured for providing DL
control signalling, and the DL control signalling is provided on one or
more of the at least two scheduling cells for a scheduled cell.

Claims:

1. A method for providing downlink (DL) control signalling for a
communication apparatus, adapted to a base station, comprising:
configuring at least two scheduling cells for providing DL control
signalling; and providing the DL control signalling on one or more of the
at least two scheduling cells for a scheduled cell.

2. The method for providing DL control signalling for a communication
apparatus according to claim 1, wherein the step of configuring the at
least two scheduling cells for providing DL control signalling comprises:
configuring a scheduling pattern for the at least two scheduling cells,
wherein the scheduling pattern indicates the scheduling cell configured
for providing DL control signalling of each subframe of the scheduled
cell.

3. The method for providing DL control signalling for a communication
apparatus according to claim 2, wherein the scheduling pattern is
configured as a bitmap.

4. The method for providing DL control signalling for a communication
apparatus according to claim 1, wherein the step of providing the DL
control signalling on the one or more of the at least two scheduling
cells for the scheduled cell comprises: providing the DL control
signalling on the scheduling cell with a highest priority for the
scheduled cell.

5. The method for providing DL control signalling for a communication
apparatus according to claim 4, wherein the priority of the at least two
scheduling cells is determined according to an index value of the
scheduling cell, a number of DL subframes configured to the scheduling
cell, an order of the scheduling cell in an UL-DL configuration index or
channel quality of the scheduling cell.

6. The method for providing DL control signalling for a communication
apparatus according to claim 1, wherein in the step of providing the DL
control signalling on the one or more of the at least two scheduling
cells for the scheduled cell, the at least two scheduling cells provide
the DL control signalling for allocating a same portion or different
portions of radio resources of a same subframe of the scheduled cell.

7. The method for providing DL control signalling according to claim 1,
wherein in the step of providing the DL control signalling on the one or
more of the at least two scheduling cells for the scheduled cell, the at
least two scheduling cells provide the DL control signalling for
different subframes of the scheduled cell.

8. The method for providing DL control signalling for a communication
apparatus according to claim 1, wherein in the step of providing the DL
control signalling on the one or more of the at least two scheduling
cells for the scheduled cell, one of the at least two scheduling cells
provide resource allocation information while another one of the at least
two scheduling cells provide an ACK/NACK feedback.

9. The method for providing DL control signalling for a communication
apparatus according to claim 1, wherein before the step of providing the
DL control signalling on the one or more of the at least two scheduling
cells for the scheduled cell, the method further comprises: sending a
message to the communication apparatus to activate the scheduled cell;
and sending the message to activate the one or more of the at least two
scheduling cells.

10. The method for providing DL control signalling for a communication
apparatus according to claim 1, wherein the step of providing the DL
control signalling on the one or more of the at least two scheduling
cells for the scheduled cell comprises: providing DL control signalling
on one of the at least two scheduling cells for the scheduled cell at a
subframe; and switching to provide DL control signalling on an another
scheduling cell of the at least two scheduling cells for the scheduled
cell at another subframe.

11. The method for providing DL control signalling for a communication
apparatus according to claim 10, wherein the step of providing the DL
control signalling on the one or more of the at least two scheduling
cells for the scheduled cell comprises: providing the DL control
signalling for the scheduled cell only when the scheduled cell is at a DL
subframe based on a UL-DL configuration configured to the scheduled cell.

12. The method for providing DL control signalling for a communication
apparatus according to claim 10, wherein the step of switching to provide
the DL control signalling on the another scheduling cell of the at least
two scheduling cells for the scheduled cell comprises: switching the
scheduling cell providing the DL control signalling among the at least
two scheduling cells based on whether the scheduling cell is at an uplink
(UL) subframe, deactivated or de-configured.

13. The method for providing DL control signalling for a communication
apparatus according to claim 1, wherein after the step of providing the
DL control signalling on the one or more of the at least two scheduling
cells for the scheduled cell, the method further comprises: switching to
transmit an ACK/NACK feedback on another scheduling cell based on whether
the scheduling cell is at an UL subframe, deactivated or de-configured.

14. The method for providing DL control signalling for a communication
apparatus according to claim 1, wherein the at least two scheduling cells
are configured with different TDD UL-DL configuration.

15. The method for providing DL control signalling for a communication
apparatus according to claim 1, wherein frame boundaries of the at least
two scheduling cells and the scheduled cell are not aligned while
subframe boundaries of the at least two scheduling cells and the
scheduled cell are aligned.

16. The method for providing DL control signalling for a communication
apparatus according to claim 1, wherein the at least two scheduling cells
adopt time division duplex (TDD) systems and the scheduled cell adopts
frequency division duplex (FDD) system.

17. The method for providing DL control signalling for a communication
apparatus according to claim 1, wherein the at least two scheduling cell
comprises the scheduled cell itself.

18. The method for providing DL control signalling for a communication
apparatus according to claim 1, wherein the DL control signalling
comprises DL and/or UL grant resource assignment information, HARQ
ACK/NACK feedbacks, a synchronization channel for DL timing
synchronization, system information, a reference signalling, or a
combination thereof.

19. A method for receiving downlink (DL) control signalling from a base
station, adapted to a communication apparatus, comprising: being
configured at least two scheduling cells for receiving DL control
signalling from the base station; and receiving the DL control signalling
on one or more of the at least two scheduling cells for a scheduled cell.

20. The method for receiving DL control signalling from a base station
according to claim 19, wherein in the step of receiving the DL control
signalling on the one or more of the at least two scheduling cells for
the scheduled cell, the method further comprises: monitoring the DL
control signalling from one of the at least two scheduling cells for the
scheduled cell at a subframe; and switching to monitor the DL control
signalling from another one of the at least two scheduling cells for the
scheduled cell at another subframe.

21. The method for receiving DL control signalling from a base station
according to claim 19, wherein the step of monitoring the scheduling cell
providing the DL control signalling comprises: monitoring the DL control
signalling for the scheduled cell only when the scheduled cell is at a DL
subframe based on a UL-DL configuration configured to the scheduled cell.

22. , The method for receiving DL control signalling from a base station
according to claim 20, wherein the step of switching to monitor another
scheduling cell providing the DL control signalling comprises: switching
to monitor the DL control signalling among the at least two scheduling
cells based on whether the scheduling cell is at an UL subframe,
deactivated or de-configured

23. The method for receiving DL control signalling from a base station
according to claim 19, wherein the step of receiving the DL control
signalling on the one or more of the at least two scheduling cells for
the scheduled cell comprises: receiving a control signalling on the
scheduling cell; and restarting an activation/deactivation timer
associated with the scheduled cell, associated with the scheduling cell
from which the control signalling is received, or associated with all
activated scheduling cells of the scheduled cell if the control
signalling indicates an UL grant or DL assignment for the scheduled cell.

24. The method for receiving DL control signalling from a base station
according to claim 19, wherein after the step of receiving the DL control
signalling on the one or more of the at least two scheduling cells for
the scheduled cell, the method further comprises: switching to receive an
ACK/NACK feedback from another scheduling cell based on whether the
scheduling cell is at an UL subframe, deactivated or de-configured.

25. A wireless communication system for providing DL control signalling,
comprising: a communication apparatus; and a base station, configured to
configure at least two scheduling cells for providing DL control
signalling to the communication apparatus, and provide the DL control
signalling on one or more of the at least two scheduling cells for a
scheduled cell.

26. The wireless communication system for providing DL control signalling
for a communication apparatus according to claim 25, wherein the base
station configures a scheduling pattern for the at least two scheduling
cells, wherein the scheduling pattern indicates the scheduling cell
configured for providing DL control signalling of each subframe of the
scheduled cell.

27. The wireless communication system for providing DL control signalling
for a communication apparatus according to claim 26, wherein the
scheduling pattern is configured as a bitmap.

28. The wireless communication system for providing DL control signalling
for a communication apparatus according to claim 25, wherein the
scheduling cell having a highest priority provides the DL control
signalling for the scheduled cell.

29. The wireless communication system for providing DL control signalling
for a communication apparatus according to claim 28, wherein the priority
of the at least two scheduling cells is determined according to an index
value of the scheduling cell, a number of DL subframes configured to the
scheduling cell, an order of the scheduling cell in an UL-DL
configuration index or channel quality of the scheduling cell.

30. The wireless communication system for providing DL control signalling
for a communication apparatus according to claim 25, wherein the at least
two scheduling cells provide the DL control signalling for allocating a
same portion or different portions of radio resources of a same subframe
of the scheduled cell.

31. The wireless communication system for providing DL control signalling
for a communication apparatus according to claim 25, wherein the at least
two scheduling cells provide the DL control signalling for different
subframes of the scheduled cell.

32. The wireless communication system for providing DL control signalling
for a communication apparatus according to claim 25, wherein one of the
at least two scheduling cells provide resource allocation information for
a subframe of the scheduled cell while another one of the at least two
scheduling cells provide an ACK/NACK feedback.

33. The wireless communication system for providing DL control signalling
for a communication apparatus according to claim 25, wherein the base
station sends a message to the communication apparatus to activate the
scheduled cell and the one or more of the at least two scheduling cells.

34. The wireless communication system for providing DL control signalling
for a communication apparatus according to claim 25, wherein the
communication apparatus monitors the DL control signalling from one of
the at least two scheduling cells for the scheduled cell at a subframe,
and switches to monitor the DL control signalling from another one of the
at least two scheduling cells for the scheduled cell at another subframe.

35. The wireless communication system for providing DL control signalling
for a communication apparatus according to claim 34, wherein the
communication apparatus monitors the DL control signalling for the
scheduled cell only when the scheduled cell is at a DL subframe based on
a UL-DL configuration configured to the scheduled cell.

36. The wireless communication system for providing DL control signalling
for a communication apparatus according to claim 34, wherein the
communication apparatus switches to monitor the DL control signalling
among the at least two scheduling cells based on whether the scheduling
cell is at an UL subframe, deactivated or de-configured.

37. The wireless communication system for providing DL control signalling
for a communication apparatus according to claim 25, wherein the
communication apparatus receiving a control signalling on the scheduling
cell, and restarts an activation/deactivation timer associated with the
scheduled cell, associated with the scheduling cell from which the
control signalling is received, or associated with all activated
scheduling cells of the scheduled cell if the control signalling
indicates an UL grant or DL assignment for the scheduled cell.

38. The wireless communication system for providing DL control signalling
for a communication apparatus according to claim 25, wherein the
communication apparatus switches to receive an ACK/NACK feedback from
another scheduling cell based on whether the scheduling cell is at an UL
subframe, deactivated or de-configured.

39. The wireless communication system for providing DL control signalling
for a communication apparatus according to claim 25, wherein the at least
two scheduling cells are configured with different TDD UL-DL
configuration.

40. The wireless communication system for providing DL control signalling
for a communication apparatus according to claim 25, wherein frame
boundaries of the at least two scheduling cells and the scheduled cell
are not aligned while subframe boundaries of the at least two scheduling
cells and the scheduled cell are aligned.

41. The wireless communication system for providing DL control signalling
for a communication apparatus according to claim 25, wherein the at least
two scheduling cells adopt TDD systems and the scheduled cell adopts FDD
system.

42. The wireless communication system for providing DL control signalling
for a communication apparatus according to claim 25, wherein the at least
two scheduling cell comprises the scheduled cell itself.

43. The wireless communication system for providing DL control signalling
for a communication apparatus according to claim 25, wherein the DL
control signalling comprises DL and/or UL grant resource assignment
information, HARQ ACK/NACK feedbacks, a synchronization channel for DL
timing synchronization, system information, a reference signalling, or a
combination thereof.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the priority benefit of U.S. provisional
application Ser. No. 61/540,548, filed Sep. 29, 2011. The entirety of the
above-mentioned patent application is hereby incorporated by reference
herein and made a part of this specification.

TECHNICAL FIELD

[0002] The disclosure relates to a method and a wireless communication
system for providing downlink control signalling for a communication
apparatus capable of receiving and/or transmitting a plurality of
component carriers.

BACKGROUND

[0003] In order to provide higher data rate transmissions and to support
various applications, telecommunication service providers continually
develop improvements in existing networks. Wider bandwidth allocation is
a way to achieve the targets. However, it is difficult to assign a wide
range contiguous spectrum for an access network due to existing
operations on certain spectra. Accordingly, it is expected that broadband
wireless access networks of next generation can be deployed by using a
combination of different spectra. Consequently, technologies supporting a
combination/concatenation of channel bandwidths to best utilize the
available spectrum should be developed to enable data transmissions over
multiple carriers. With the application of a scheme referred to as
Carrier Aggregation or Multiple "Component Carriers" (CCs), networks can
be enabled to operate over continuous or discontinuous carriers having
different bandwidths.

[0004] The carrier aggregation scheme may utilize separate FFT and radio
frequency (RF) modules for each individual band. Based on user
capabilities, network entities (e.g. a base station (BS), a Node-B, an
eNode-B, a base transceiver system (BTS), an access point (AP), a home
base station, a relay station, a scatterer, a repeater, an intermediate
node, an intermediary, and/or satellite-based communication base station,
etc.) can serve different users with corresponding different bandwidths.
With the support of multiple CCs, a BS can flexibly use limited bandwidth
to achieve high throughput to improve user experience at the user
equipment (UE).

[0005] In Carrier Aggregation (CA), two or more component carriers (CCs)
or cells can be aggregated in order to support wider transmission
bandwidths. A UE can simultaneously receive or transmit one or multiple
CCs depending on its capabilities. A UE may be configured with more than
one Cell. One of them is Primary Cell (PCell), and the other(s) is/are
secondary cell(s) (SCell).

[0006] For example, FIG. 1 illustrates a conventional LTE TDD UL-DL
configuration table. As shown in FIG. 1, there are 7 UL/DL configurations
supported in LTE TDD systems, in which a LTE TDD system with TDD DL/UL
subframe configuration#0 implies that Subframes 0 and 5 are DL subframes;
Subframes 1 and 6 are SPECIAL subframes; and Subframe 2, 3, 4, 7, 8, 9
are UL subframes.

[0007]FIG. 2 illustrates a DL ACK/NACK Timing in TDD. For PUSCH
transmissions scheduled from a serving cell c in subframe n, a UE shall
determine the corresponding PHICH resource of serving cell c for
receiving ACK/NACK feedbacks for PUSCH transmissions in subframe
n+kPHICH, where kPHICH is given in the table of FIG. 2.

[0008] On the other hand, cross-carrier scheduling is introduced for
carrier aggregation in LTE Rel-10. FIG. 3 is a schematic diagram
illustrating cross-carrier scheduling. Referring to FIG. 3, cross-carrier
scheduling is configured to allow the control signalling (PDCCH) of a
serving cell to schedule resources on another serving cell (e.g., The
PDCCH of the CC#2 schedules resources for CC#3) in order to reduce PDCCH
channel interference. In this example, CC#2 is the scheduling cell of the
CC#3, and the CC#3 is called scheduled cell. Carrier indicator field
(CIF) included in the PDCCH of the scheduling cell indicates the cell
identity (e.g., CellIndex) of the scheduled cell. When the PDCCH of a
SCell is configured, cross-carrier scheduling does not apply to this
SCell since this SCell is always scheduled via its PDCCH. However, when a
CA-capable UE is configured with two cells with different TDD UL-DL
configuration, the following issues may need to take into consideration.

[0009] The first issue is: no PDCCH on the Scheduling Cell for DL or UL
resource assignments. To be specific, when a CA-capable UE is configured
with two cells with different TDD UL-DL configuration, some DL resources
on the scheduled cell can not be allocated to the UE, because there is no
PDCCH on the scheduling cell for cross-carrier scheduling. FIG. 4
illustrates an example of no PDCCH on the Scheduling Cell for DL and UL
resource assignments. In this example, the scheduling Cell of the Cell#3
for a UE is the PCell (Cell#0). In other words, the DL resource of the
Cell#3 at the subframe#4 shall be allocated by the subframe #4 of the
PCell. However, PCell's subframe#4 is a UL subframe and there is no
available DL resource that can be used for cross-carrier scheduling.
Thus, the subframe#4 on Cell#3 can't be used by the UE, and the UE can't
fully use the bandwidth of the aggregated Cell#3.

[0010] The second issue is on HARQ ACK/NACK feedback timing. FIG. 5
illustrates an example of HARQ ACK/NACK feedback timing. As illustrated
in FIG. 5, based on HARQ ACK/NACK timing (e.g., illustrated in FIG. 2),
the corresponding subframe on the scheduling cell to reply HARQ ACK/NACK
for the previous PUSCH transmitted on the scheduled cell is an UL
subframe. In other words, there is no DL resource to send the HARQ
ACK/NACK. Thus, the UE needs to re-transmit the UL data again, because no
ACK is received.

[0011] Accordingly, there is a need to develop a new scheme to provide
downlink control signalling for the UE, which is configured with multiple
TDD cells with different UL-DL configurations.

SUMMARY

[0012] According to an example of the disclosure, a method for providing
downlink (DL) control signalling for a communication apparatus is
provided. In the method, at least two scheduling cells are configured for
providing DL control signalling, and the DL control signalling is
provided on one or more of the at least two scheduling cells for a
scheduled cell.

[0013] According to an example of the disclosure, a wireless communication
system for providing DL control signalling is provided. The system
comprises a communication apparatus and a base station. The base station
is configured to configure at least two scheduling cells for providing DL
control signalling to the communication apparatus, and provide the DL
control signalling on one or more of the at least two scheduling cells
for a scheduled cell.

[0014] Several exemplary examples accompanied with figures are described
in detail below to further describe the disclosure in details.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings are included to provide further
understanding, and are incorporated in and constitute a part of this
specification. The drawings illustrate exemplary examples and, together
with the description, serve to explain the principles of the disclosure.

[0030]FIG. 6 is a schematic diagram illustrating the wireless
communication system for providing DL control signalling for a
communication apparatus according to an example of the disclosure.
Referring to FIG. 6, in the wireless communication system 60, the
communication apparatus 64 may have a plurality of cells (e.g., Cell#1 to
Cell#3), and the base station 62 may configure communication apparatus 64
with at least two scheduling cells (i.e., Cell#1 & Cell#2) and those
scheduling cells may provide DL control signalling for the scheduled cell
(i.e., Cell#3).

[0031] It is noted that, in the disclosure, 3GPP-like keywords are used to
present the ideas; however, those ideas could be applied to other systems
(e.g., IEEE 802.11, IEEE 802.16, WiMAX, etc.), which are not limited
herein. In the disclosure, the term "cell" is used to represent a
component carrier (CC), which may be operated on a frequency division
duplex (FDD) and/or a time division duplex (TDD) system. The cell may
have downlink resource to transmit signals from the base station (BS) to
the communication apparatus, and/or may have uplink resource to transmit
signals from the communication apparatus to the base station. For
example, the term "PCC" may be equivalent to the term "Primary Cell
(PCell)", and the term "SCC" may be equivalent to the term "Secondary
Cell (SCell)".

[0032] Multiple cells may operate on the same or different frequency band,
and may have the same or different center frequency. Multiple cells may
belong to the same base station or different base stations. The term
"base station (BS)" in this disclosure may be, for example, a Node-B, an
eNode B, a base transceiver system (BTS), an access point, a home base
station, a relay station, a scatterer, a repeater, an intermediate node,
an intermediary, and/or satellite-based communication base station, etc.

[0033] The communication apparatus 64 may be, for example, a server, a
client, a desktop computer, a laptop computer, a network computer, a
workstation, a personal digital assistant (PDA), a tablet, a scanner, a
telephony device, a pager, a camera, a television, a hand-held video game
device, a musical device, a wireless sensor, or any other user equipment
(UE). In some applications, the communication apparatus 64 may be a fixed
computing device operated in a mobile environment, such as a bus, a
train, an airplane, a boat, a car, etc.

[0034]FIG. 7 is a flowchart illustrating a method for providing DL
control signalling for a communication apparatus according to an example
of the disclosure. The method of this example is applicable to the
wireless communication system 60 of FIG. 6, and detailed steps of the
method are illustrated below in cooperation with elements in the wireless
communication system 60.

[0035] First of all, the base station 62 may configure at least two
scheduling cells for providing DL control signalling to the communication
apparatus 64 (step S702). The scheduling cell of a cell may be the cell
itself. For example, referring to FIG. 3, the PDCCH and/or PHICH of
cell#2 may provide DL control signalling for the cell#2 itself.

[0036] In step S702, the base station 62 (e.g., eNodeB) may send a message
(e.g., a RRC message (RRCConnectionReconfiguration)) to configure (or
add) a scheduled cell for the communication apparatus 64. The base
station 62 may configure at least two scheduling cells for the
communication apparatus 64 (e.g., in the same (RRC) message). The
scheduling cell provides DL control signalling for a scheduled cell. The
DL control signalling may include at least one of the following
parameters.

[0042] The PDCCH of a scheduling cell may dynamically allocate resources
(e.g., physical resource blocks (PRBs) and modulation coding schemes
(MCS)) for one or more cells. Thus, an indication (e.g., carrier
indicator field (CIF)) may be included in the PDCCH of the scheduling
cell to indicate the cell identity (e.g., CellIndex) of the scheduled
cell. The scheduling cells and/or scheduled cell may have same or
different duplex mode (e.g., FDD or TDD) and may have same or different
UL-DL configuration, which is not limited herein.

[0043] In an example, the base station 62 may configure communication
apparatus 64 with at least two scheduling cells for a scheduled cell. For
example, the base station 62 may configure cell#1 and cell#2 to be the
scheduling cell of cell#3, and these two scheduling cells may work for
the same subframe. In another example, the base station 62 may configure
communication apparatus 64 with a first scheduling cell for the cell#1
and a second scheduling cell for the cell#2, in which the second
scheduling cell may sometimes be the scheduling cell of the cell#1. In
other words, the two scheduling cells may provide DL control signalling
for the scheduled cell for the same subframe (e.g., at the same time
(TTI)), and/or for different subframes (e.g., the scheduling cell for the
scheduled cell is time dependent). In yet another example, the scheduling
cells may work for the same subframes at some TTIs, and may work for
different subframes at the other TTIs.

[0044] It is noted that, after the scheduling cells and the scheduled cell
are configured, the base station 62 may send a message (e.g., an
Activation/Deactivation MAC control element) to the communication
apparatus 64 so as to activate the scheduled cell. The base station 62
may also activate at least a scheduling cell for the scheduled cell
(e.g., if none of the scheduling cells for the scheduled cell has been
activated). When receiving the message, the communication apparatus 64
may activate the cell. For example, the communication apparatus 64 may
execute following actions for an activated cell.

[0049] Once the scheduled cell is activated, the base station 62 may
provide the DL control signalling on one or more of the at least two
scheduling cells for the scheduled cell (step S704). However, the
communication apparatus 64 may not need to monitor DL control signalling
for the scheduled cell at each subframe (and at each TTI). In some
embodiments, the communication apparatus 64 may determine whether to
monitor DL control signalling on the scheduling cell at a TTI based on
the UL-DL configuration of the scheduled cell. In an example, the
communication apparatus 64 may monitor DL control signalling for the
scheduled cell at the time only when the scheduled cell has DL resources
(i.e. at a DL subframe). That is, the communication apparatus 64 may not
monitor DL control signalling on the scheduling cell for the scheduled
cell at the TTI when the scheduled cell has only UL. In another example,
when the timealignmenttimer is not running, the communication apparatus
64 may not monitor DL control signalling for the scheduled cell at the
time when the scheduled cell has only UL (i.e. at a UL subframe). But,
when the timealignmenttimer is running, the communication apparatus 64
may monitor DL control signalling for the scheduled cell no matter the
scheduled cell is at a DL or UL subframe. It is noted that if the PDCCH
on a scheduling cell indicates UL grant or DL assignment for the
scheduled cell, the communication apparatus 64 may restart the
corresponding timer(s) (e.g., sCellDeactivationTimer) associated with
corresponding cell(s). Examples of the base station configuring the
scheduling cells and the communication apparatus monitoring the DL
control signalling are provided below for further illustration.

EXAMPLE 1

[0050]FIG. 8 is an example of a method for providing DL control
signalling for a communication apparatus according to an example of the
disclosure. In this example, the base station may configure two
scheduling cells for a scheduled cell having a UL-DL configuration#1. One
is primary scheduling cell having a UL-DL configuration#3, and the other
is secondary scheduling cell having a UL-DL configuration#2. The
communication apparatus may receive a message to activate these two
scheduling cells and the scheduled cell. Then, the communication
apparatus may monitor DL control signalling (e.g., PDCCH and/or PHICH) on
the primary scheduling cell for the scheduled cell at some TTIs (e.g. TTI
82), and switch to monitor DL control signalling on the secondary
scheduling cell for the scheduled cell at some TTIs (e.g. TTI 84) when
there is no available DL resource (e.g., PDCCH and/or PHICH) on the
primary scheduling cell. To be specific, at TTI 84, the primary
scheduling cell may be in a UL subframe, or the primary scheduling cell
is deactivated or de-configured (removed).

EXAMPLE 2

[0051]FIG. 9 is an example of a method for providing DL control
signalling for a communication apparatus according to an example of the
disclosure. In this example, the base station may configure at least two
scheduling cells (e.g. a scheduling cell#1 and a scheduling cell#2) for
providing DL control signalling of a scheduled cell. When receiving a
message to activate the scheduling cells #1 and #2 and the scheduled
cell, the communication apparatus may monitor DL control signalling on
the scheduling cell with highest priority (among all "activated" and/or
"DL-available" scheduling cells) for the scheduled cell. The "priority"
may be determined by at least one of the following criteria:

[0052] a. the priority of a scheduling cell may be assigned/configured by
the base station when the Cell is added or configured;

[0053] b. a cell having a smaller cell_index (e.g, CellIndex, SCellIndex)
may has higher priority, in which each cell may be configured with an
apparatus-specific cell_index, and the PCell may have the smallest
cell_index (e.g., 0);

[0054] c. a cell which is configured with more DL subframes may have
higher priority;

[0055] d. the TDD UL-DL configuration index is used to prioritize the
cells; and

[0057] Referring to FIG. 9, DL HARQ ACK/NACK feedback is illustrated. In
this example, the DL ACK/NACK feedbacks may be not sent from the
scheduling cell where the corresponding UL grant is assigned, but from
the scheduling cell which has available DL subframe (or PHICH) at some
TTIs. In this example, the scheduling cell having a smaller cell_index is
assigned to have higher priority. Then, the communication apparatus may
monitor PDCCH at subframe #x on scheduling cell#1 (i.e. with higher
priority) for the UL grant at subframe #y on the scheduled cell. If the
communication apparatus sends a UL transmission on scheduled cell at
subframe #y, the communication apparatus may expect to receive the
corresponding HARQ ACK/NACK feedback at subframe #z. The communication
apparatus may monitor the PHICH at subframe #z on the scheduling cell#2
(i.e., with higher priority) to receive the HARQ ACK/NACK feedback for
the UL transmission at subframe #y, and/or may monitor PDCCH on the
scheduling cell#2 (with higher priority) to receive DL resource
allocation information at subframe #z for the scheduled cell.

EXAMPLE 3

[0058] In this example, the base station may configure one scheduling cell
for a scheduled cell first. When the scheduled cell is activated, the
communication apparatus may monitor the DL control signalling on the
scheduling cell for the scheduled cell. When there is no available DL
resource on the configured scheduling cell at a TTI (e.g., the scheduling
cell has only UL resource at this TTI or the scheduling cell is
deactivated or de-configured), the communication apparatus may monitor DL
control signalling on another pre-defined "backup" cell for the scheduled
cell. For example, the communication apparatus may switch to monitor the
DL control signalling on the backup cell when the scheduling cell has
only UL subframe at the TTI or when the primary scheduling cell is
deactivated or de-configured (removed). The backup cell may be a PCell or
the scheduled cell itself, and may be indicated by the base station
through a message (e.g., by which the SCell is configured (added) to the
communication apparatus).

EXAMPLE 4

[0059] In this example, the base station may configure one scheduling cell
for a scheduled cell first. When the scheduled cell is activated, the
communication apparatus may monitor the DL control signalling on the
scheduling cell for the scheduled cell. When there is no available DL
resource on the configured scheduling cell for the scheduled cell at a
TTI (e.g., the scheduling cell has only UL resource at this TTI or the
scheduling cell is deactivated or de-configured), another scheduling cell
which may be configured for scheduling other scheduled cell may become
the scheduling cell of the scheduled cell (for this TTI). The
communication apparatus may need to determine which cell becomes the
scheduling cell for the scheduled cell at this TTI. In some embodiments,
the determination may be based on a priority. In one example, a
pre-defined priority order is given in RRC message. In another example,
the cell may have a highest priority if it has a smallest cell index
among the scheduling cells having available DL subframe (or PDCCH) at
this TTI. In some embodiments, the determination may be based on the
configured DL resources. For example, the scheduling cell which is
configured with more DL subframes may become the new scheduling cell of
the scheduled cell. In some embodiments, the determination may be based
on the channel condition. For example, the scheduling cell having a
better channel condition (e.g., CQI, PMI, RI, PTI, BER, RSRP, RSRQ, . . .
, etc.) may become the new scheduling cell of the scheduled cell.

EXAMPLE 5

[0060]FIG. 10 is an example of a method for providing DL control
signalling for a communication apparatus according to an example of the
disclosure. In this example, the base station may configure at least two
scheduling cells (e.g. a scheduling cell#1 and a scheduling cell#2) for a
scheduled cell, in which the scheduling cells #1 and #2 may provide
different DL control signalling for the scheduled cell at the same
subframe (at the same TTI). Referring to FIG. 10, both scheduling cells
#1 and #2 provide DL control signalling for the scheduled cell#3 at the
same time. In some embodiments, the two DL control signalling indicate
two different portions of radio resources of a subframe. In an example,
these two portions of radio resources may be used to transmit different
data packet. In another example, these two portions of radio resources
may be used to transmit the same data packet, or transmit different
redundancy versions (e.g., HARQ Redundancy version #0, #1, #2, #3) of the
same data packet.

[0061] In another embodiment, both scheduling cells provide only a part of
DL control information for the scheduled cell at the same subframe. The
communication apparatus may combine the DL control signalling from the
scheduling cells together to get complete DL control information for the
scheduled cell. Since the DL channel capacity is limited, the DL control
information may be separately transmitted on the two scheduling cells.
For example, one scheduling cell may provide the PDCCH (i.e., radio
resource allocation information such as DL assignment and/or UL grant
assignment), and the other scheduling cell may provide the PHICH (i.e.,
HARQ ACK/NACK feedbacks). In another example, the communication apparatus
may receive DL control signalling from both scheduling cells and perform
signalling combing on the received DL control signalling, so as to
increase the reliability of the received DL control information. In
brief, the communication apparatus may monitor DL control signalling on
all (activated) scheduling cells for the scheduled cell.

EXAMPLE 6

[0062] FIG. 11 is an example of a method for providing DL control
signalling for a communication apparatus according to an example of the
disclosure. In this example, the base station may configure at least two
scheduling cells (e.g. a scheduling cell#1 and a scheduling cell#2) for a
scheduled cell, in which the scheduling cells #1 and #2 may provide the
same DL control signalling for the scheduled cell at the same subframe.
Referring to FIG. 11, both scheduling cells #1 and #2 indicate the same
DL control information (e.g., DL and/or UL resource assignment
information, HARQ ACK/NACK feedbacks, etc.) for the scheduled cell#3, so
as to increase PDCCH reliability. In another example, the communication
apparatus may not need to monitor or decode all scheduling cells, if the
communication apparatus has successfully received or decoded the DL
control information from one scheduling cell. In yet another example, the
communication apparatus may receive DL control signalling from both
scheduling cells #1 and #2, perform signalling combing on the received DL
control signalling, and decode the combined DL control information for
the scheduled cell, so as to reduce the error rate of DL control channel.

EXAMPLE 7

[0063] In this example, the base station may configure at least two
scheduling cells for a scheduled cell, in which the base station may
configure a scheduling pattern for each scheduling cell for the scheduled
cell. The scheduling pattern may indicate the communication apparatus
which subframes the base station may send DL control signalling on the
corresponding scheduling cell for the scheduled cell. In an example, the
scheduling pattern may include a bitmap, in which each bit in the bitmap
indicates whether there may be DL control signalling at the corresponding
subframe on the corresponding scheduling cell. In another example, the
scheduling pattern may indicate that a scheduling cell #1 provides DL
control signalling for the scheduled cell at odd subframes, and a
scheduling cell #2 provides the DL control signalling for the scheduled
cell at even subframes. This scheduling pattern may be configured by the
same SCell configuration message (e.g., RRCConnectionReconfiguration), by
which the scheduled cell is configured (or added) to the communication
apparatus. When the scheduled cell is active, the communication apparatus
may monitor DL control signalling on (activated) scheduling cells for
scheduled cell based on the scheduling pattern.

EXAMPLE 8

[0064] The disclosure could be used not only for CA with different TDD
UL-DL configurations, but also for CA with the same TDD UL-DL
configuration. For example, FIG. 12 is an example of a method for
providing DL control signalling for a communication apparatus according
to an example of the disclosure. In this example, carrier aggregation
with the same TDD UL-DL configuration is illustrated. The frame boundary
between aggregated cells (e.g. scheduling cells #1 and #2 and scheduled
cell #3) may be not aligned or synchronized, but the subframe boundary
may be aligned. Of course, the disclosure can be applied to different TDD
UL-DL configurations without frame boundary alignment. In this example,
the communication apparatus may monitor DL control signalling on
scheduling cell #1 for scheduled cell #3 at TTI 122, and switch to
monitor DL control signalling on scheduling cell #2 for scheduled cell #3
at TTI 124 when there is no available DL resource (e.g., PDCCH and/or
PHICH) on the scheduling cell #1.

EXAMPLE 9

[0065] The disclosure could be used for TDD and FDD combined carrier
aggregation. In this example, the communication apparatus is configured
with two cells. One adopts time division duplex (TDD) system and the
other adopts frequency division duplex (FDD) system. All of previous
examples could apply. For example, FIG. 13 is an example of a method for
providing DL control signalling for a communication apparatus according
to an example of the disclosure. Referring to FIG. 13, the scheduled cell
#3 adopts a FDD system, and the scheduling cells #1 and #2 adopt TDD
system and have different UL-DL configurations (i.e. UL-DL configurations
#3 and #5). In this example, the communication apparatus may monitor DL
control signalling on scheduling cell #1 for scheduled cell #3 at TTI
132, and switch to monitor DL control signalling on scheduling cell #2
for scheduled cell #3 at TTI 134 when there is no available DL resource
(e.g., PDCCH and/or PHICH) on the scheduling cell #1.

[0066] It is noted that when the DL control signalling is detected, if the
PDCCH received on the scheduling cell indicates an UL grant or DL
assignment for the scheduled cell, the communication apparatus may
restart the activation/deactivation timer (e.g., sCellDeactivationTimer)
associated with the scheduled cell, and/or restart the timer (e.g.,
sCellDeactivationTimer) associated with the scheduling cell from which
the PDCCH is received. In another example, the communication apparatus
may restart the timer (e.g., sCellDeactivationTimer) associated with all
(activated) scheduling cell(s) of the scheduled cell.

[0067] When the timer (e.g., sCellDeactivationTimer) associated with the
activated cell expires and/or the communication apparatus receives a
message (e.g., Activation/Deactivation MAC control element) to deactivate
the cell from the base station, the communication apparatus may
deactivate the Cell, stop the timer (e.g., sCellDeactivationTimer)
associated with the cell, flush all HARQ buffers associated with the
Cell, not transmit SRS on the Cell, not report CQI/PMI/RI/PTI for the
Cell, not transmit on UL-SCH on the Cell, stop on going Random Access
procedure on the Cell, not monitor DL control signalling (e.g., PDCCH) on
corresponding scheduling Cell(s) for the Cell, or perform a combination
of aforesaid actions. If the communication apparatus receives a message
(e.g., RRCConnectionReconfiguration message) to de-configure (or remove)
a cell from the base station, the communication apparatus may de-activate
and/or de-configure (remove) the cell.

[0068] As described above, in the method and the system for providing DL
control signalling for a communication apparatus of the disclosure,
multiple scheduling cells with the same or different UL-DL configurations
are configured to provide DL control signalling for a scheduled cell, in
which the scheduling cells may work for the same or different subframes.
Accordingly, the scheduling cells for providing the DL control signalling
can be dynamically changed, and the base station can flexibly use limited
bandwidth to achieve high throughput and capacity.

[0069] It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the
disclosed examples without departing from the scope or spirit of the
disclosure. In view of the foregoing, it is intended that the disclosure
cover modifications and variations of this disclosure provided they fall
within the scope of the following claims and their equivalents.